Hello @bhthomas ,
What appears to be happening here is that your canvas document has been moved-partially off-screen/out of the viewport. Since the document background is a shade of grey very similar to the shade of the viewport background, it is difficult to make out where the document ends and that UI backdrop begins.
Remember that ZBrush is a hybrid 2D/3D program. It is similar to Photoshop in that there is an actual sized document that can be moved around the UI window.
Try this. Go to the Document palette and increase the “Range” (Background Gradient Range) slider to .5 or so. This will create a gradient shading to the document background that will make it easier to separate from the UI background. You can then slide that document around the viewport using the Scroll button at the top right of the default UI viewport frame, in the Document palette, or in the spacebar pop-up. This is a 2D function that only affects the document, and does not actually move the camera itself around.
